The highly rated 20-year-old became a regular for Les Girondins at the age of just 17 but last season found chances hard to come by under former Red Devils defender Laurent Blanc.
The French Under-21 international was loaned out to fellow Ligue 1 side Lorient for the second half of last season where he featured 15 times scoring just the one goal.
"There is a very strong likelihood that the deal will go ahead," confirmed Triaud to L'Equipe.
"Manchester United want to sign him and, for our part, we would be delighted to see Gabriel playing for such a prestigious club.
"We will make the official announcement when the time is right."